How do I create a completely unattended install of Ubuntu?

The complete solution is:

Remaster a CD, ie, download a non graphical ubuntu installation ISO (server or alternate installation CD), mount it

$ sudo su -
# mkdir -p /mnt/iso
# mount -o loop ubuntu.iso /mnt/iso

Copy the relevant files to a different directory

# mkdir -p /opt/ubuntuiso
# cp -rT /mnt/iso /opt/ubuntuiso

Prevent the language selection menu from appearing

# cd /opt/ubuntuiso
# echo en >isolinux/lang

Use GUI program to add a kickstart file named ks.cfg

# apt-get install system-config-kickstart
# system-config-kickstart # save file to ks.cfg

To add packages for the installation, add a %package section to the ks.cfg kickstart file, append to the end of ks.cfg file something like this.

%packages
@ ubuntu-server
openssh-server
ftp
build-essential

This will install the ubuntu-server "bundle", and will add the openssh-server, ftp and build-essential packages.

Add a preseed file, to suppress other questions

# echo 'd-i partman/confirm_write_new_label boolean true
d-i partman/choose_partition \
select Finish partitioning and write changes to disk
d-i partman/confirm boolean true' > ks.preseed

Set the boot command line to use the kickstart and preseed files

# vi isolinux/txt.cfg

Search for

label install
  menu label ^Install Ubuntu Server
  kernel /install/vmlinuz
  append  file=/cdrom/preseed/ubuntu-server.seed vga=788 initrd=/install/initrd.gz quiet --

add ks=cdrom:/ks.cfg and preseed/file=/cdrom/ks.preseed to the append line. You can remove the quiet and vga=788 words. It should look like

  append file=/cdrom/preseed/ubuntu-server.seed \
     initrd=/install/initrd.gz \
     ks=cdrom:/ks.cfg preseed/file=/cdrom/ks.preseed --

Now create a new iso

# mkisofs -D -r -V "ATTENDLESS_UBUNTU" \
     -cache-inodes -J -l -b isolinux/isolinux.bin \
     -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 \
     -boot-info-table -o /opt/autoinstall.iso /opt/ubuntuiso

That's it. You'll have a CD that would install an Ubuntu system once you boot from it, without requiring a single keystroke.


The instructions at this question cover the process for creating an EFI bootable ISO (like the official Ubuntu x86_64 ISO).:

How do I create an EFI-bootable ISO of a customized version of Ubuntu?

The key differences are setting this as the preseed file:

d-i partman-auto/method string lvm
d-i partman-auto-lvm/guided_size string max
d-i partman-auto/choose_recipe select atomic
d-i partman-partitioning/confirm_write_new_label boolean true
d-i partman/confirm_write_new_label     boolean true
d-i partman/choose_partition            select  finish
d-i partman/confirm_nooverwrite         boolean true
d-i partman/confirm                     boolean true
d-i partman-auto/purge_lvm_from_device  boolean true
d-i partman-lvm/device_remove_lvm       boolean true
d-i partman-lvm/confirm                 boolean true
d-i partman-lvm/confirm_nooverwrite     boolean true
d-i partman-auto/init_automatically_partition       select      Guided - use entire disk and set up LVM
d-i partman/choose_partition                select      Finish partitioning and write changes to disk
d-i partman-auto-lvm/no_boot            boolean true
d-i partman-md/device_remove_md         boolean true
d-i partman-md/confirm                  boolean true
d-i partman-md/confirm_nooverwrite      boolean true

Use this as the kickstart file:

lang en_US
langsupport en_US
keyboard us
mouse
timezone America/Los_Angeles
rootpw --disabled
user USERNAME --fullname "USERNAME" --password "PASSWORD"
reboot
text
install
cdrom
auth  --useshadow  --enablemd5 
network --bootproto=dhcp --device=eth0
firewall --disabled 
skipx
%packages
@ ubuntu-server
openssh-server

Edit the grub EFI boot configuration for the ISO:

sudo nano ~/ubuntu/boot/grub/grub.cfg

Set to:

if loadfont /boot/grub/font.pf2 ; then
    set gfxmode=auto
    insmod efi_gop
    insmod efi_uga
    insmod gfxterm
    terminal_output gfxterm
fi

set menu_color_normal=white/light-blue
set menu_color_highlight=light-blue/light-gray
set timeout=10
set default=0

menuentry "Automatically Install Ubuntu Server with Custom Config" {
    set gfxpayload=keep
    linux   /install/vmlinuz  file=/cdrom/preseed/ubuntu-server.seed quiet ks=cdrom:/ks.cfg preseed/file=/cdrom/ks.preseed --
    initrd  /install/initrd.gz
}
menuentry "OEM install (for manufacturers)" {
    set gfxpayload=keep
    linux   /install/vmlinuz  file=/cdrom/preseed/ubuntu-server.seed quiet oem-config/enable=true --
    initrd  /install/initrd.gz
}
menuentry "Multiple server install with MAAS" {
    set gfxpayload=keep
    linux   /install/vmlinuz  modules=maas-enlist-udeb vga=788 initrd=/install/initrd.gz quiet --
    initrd  /install/initrd.gz
}
menuentry "Check disc for defects" {
    set gfxpayload=keep
    linux   /install/vmlinuz  MENU=/bin/cdrom-checker-menu quiet --
    initrd  /install/initrd.gz
}
menuentry "Rescue a broken system" {
    set gfxpayload=keep
    linux   /install/vmlinuz  rescue/enable=true --
    initrd  /install/initrd.gz
}

Set isolinux/txt.cfg like this:

default install
label install
  menu label ^Install Ubuntu Server with Custom Config
  kernel /install/vmlinuz
  append file=/cdrom/preseed/ubuntu-server.seed initrd=/install/initrd.gz ks=cdrom:/ks.cfg preseed/file=/cdrom/ks.preseed --
label cloud
  menu label ^Multiple server install with MAAS
  kernel /install/vmlinuz
  append   modules=maas-enlist-udeb vga=788 initrd=/install/initrd.gz quiet --
label check
  menu label ^Check disc for defects
  kernel /install/vmlinuz
  append   MENU=/bin/cdrom-checker-menu vga=788 initrd=/install/initrd.gz quiet --
label memtest
  menu label Test ^memory
  kernel /install/mt86plus
label hd
  menu label ^Boot from first hard disk
  localboot 0x80

Create a dual boot catalog ISO:

sudo mkisofs -U -A "Custom1404" -V "Custom1404" -volset "Custom1404" -J -joliet-long -r -v -T -o ../Custom1404.iso -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -eltorito-alt-boot -e boot/grub/efi.img -no-emul-boot .

Verify an EFI-bootable ISO has been created:

dumpet -i Custom1404.iso 

Outputs:

Validation Entry:
    Header Indicator: 0x01 (Validation Entry)
    PlatformId: 0x00 (80x86)
    ID: ""
    Checksum: 0x55aa
    Key bytes: 0x55aa
Boot Catalog Default Entry:
    Entry is bootable
    Boot Media emulation type: no emulation
    Media load segment: 0x0 (0000:7c00)
    System type: 0 (0x00)
    Load Sectors: 4 (0x0004)
    Load LBA: 3100 (0x00000c1c)
Section Header Entry:
    Header Indicator: 0x91 (Final Section Header Entry)
    PlatformId: 0xef (EFI)
    Section Entries: 1
    ID: ""
Boot Catalog Section Entry:
    Entry is bootable
    Boot Media emulation type: no emulation
    Media load address: 0 (0x0000)
    System type: 0 (0x00)
    Load Sectors: 4672 (0x1240)
    Load LBA: 1932 (0x0000078c)

Here is a shell script which performs this procedure, thanks for the introduction: http://www.utech.de/2013/05/shell-script-creating-a-cd-for-unattended-ubuntu-server-installations/

The script you find following the link basically implements the procedure that @Elazar described, so the essential parts are just a screen above. I added the link to save somebody some time, and to make it a bit easier to repeat this for other versions of Ubuntu.